<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    div::before{ /*before 和 after 在盒子内部的前面插入或者在盒子的后面插入*/
      content: "俺";
    }
    div::after {
      content: "18岁";
    }
  </style>
</head>
<body>
  <div>今年</div>
</body>
</html>
